The invention relates to an allergen-inhibiting encasing for receiving objects contaminated with respirable fine dust and extremely fine dust, house dust, moulds and allergens, e.g. excretions of house dust mites, together with air, especially bedding and/or upholstery of all kinds. The encasing has at least one web of woven fabric or nonwoven and a mechanical closure such as a zip fastener, in a configuration blocking the passage of allergens and extremely fine dust.
With allergen-inhibiting encasings intended to receive the aforementioned objects, the encasings must on the one hand be air-permeable to a limited extent and on the other hand are to prevent contamination of the surrounding air with respirable fine or extremely fine dust and allergens. It is, inter alia, necessary to clean the encasing in regular intervals. For this reason, such encasings must be provided with a suitable closure system which is easy to handle, suitable for repeated use and likewise allergen-inhibiting. It must be capable of diminishing the excess pressure, which occasionally occurs within the encasing upon volume reduction such as that caused by pushing or kneading movements. Preferably, the diminishing of the excess pressure should be gradual enough for the sudden change of pressure both in the region of the textile web as well as of the closure systems to be uniformly low, so that no respirable fine dust and allergens may be emitted thereby.
It is known to provide an almost air-impermeable encasing for bedding and upholstery with a zip fastener which can, in addition, be sealed by means of a pressure-sensitive adhesive tape suitable for multiple repeated closing. To this end, the constitution of the web material must have comparatively satisfactory air permeability with simultaneous particle impermeability to respiratory fine dust in the range of  less than 10 xcexcm (U.S. Pat. No. 5,321,861).
In WO 96/21379 there is described an allergen-inhibiting encasing wherein the upper part of the enclosed space consists of a dense, coated material, whereas the bottom side consists only of a dense material whose air impermeability is greater than that of the zip fastener and through which air can emerge more easily than through the zip fastener. Here, too, however, the prerequisite must be met that the fabric of the bottom side has a comparatively high particle imperviousness to respirable fine dust.
In EP 0 600 459 A1 there is described an allergen-inhibiting encasing with a zip fastener of a polyethylene nonwoven (Tyvek) wherein at least one overlapping portion of the web in front of and/or behind the zip fastener is intended to provide a reliable seal. To achieve this it would, however, in any case be necessary for the far-projecting, overlapping web portions to rest planar with the zip fastener to be sealed, both against the inner face as well as against the outer face of the encasing, which, given the common use of bedding, is frequently not the case.
A difficulty of all known solutions is that the web material which is to be used for the allergen-inhibiting encasing must on the one hand possess a comparatively high permeability to air and water vapor and on the other hand a high degree of impermeability to particles. These requirements are contradictory in terms of physics since high air permeability is inevitably connected with a reduction of the particle impermeability. Insufficient particle impermeability can lead to respiratory tract symptoms as a result of aerogenic contact with extremely fine dust loaded with allergens of the aforementioned type, and as a result of emerging natural rubber latex products. Here, the trigger substances are proteins which attach to dust particles and which to a substantial extent are present in particle sizes smaller than 1 xcexcm.
It is the object of the present invention to configure an allergen-inhibiting encasing such that a material of a web of the encasing filters out particle sizes of smaller than 1 xcexcm and thus inevitably has a comparatively low air permeability. A closure system of the encasing at the same time is configured such that on the one hand it can be repeatedly operated many times and thus prevents the occurrence, upon ejection of air, of an increased flow rate through the closure system, with the result that allergenic dust and extremely fine particles are not emitted in concentrations above the permissible or acceptable limits, while the encasing nevertheless has a satisfactory water vapor permeability which markedly improves sleeping comfort. This also prevents the formation of moulds due to accumulation of moisture in the interior of the encasing.